The time marking the midpoint of the response window.
<block> <defaults> <expt> <likert> <openended> <response> <slidertrial> <trial>
The following displays the value of windowcenter in a text stimulus:
<text sometext>
/ items= ("windowcenter = <% response.foo.windowcenter %>")
</text>
The following displays the value of windowcenter in an instruction page:
<page somepage>
windowcenter = <% response.bar.windowcenter %>
</page>